There has been strong opposition to the merger plans, which ministers say will make the police more effective.

Ministers have delayed the plans saying there will be no forced mergers before next April.

The mergers could see the number of forces cut from 43 to as few as 17 but new Home Secretary John Reid says he wants to take more time to decide the details.

The voluntary merger of the Lancashire and Cumbria forces is due to go ahead on 1 April next year.

Neighbourhood policing?

Conservative and Liberal Democrat peers secured the fresh victory over the government by passing an amendment to the Police and Justice Bill.

Laws passed in 1996 mean police forces can be merged if the home secretary thinks it is efficient or if the police authorities, made up of councillors, magistrates and other local people, want it to happen.

But the new amendment would allow mergers to go ahead only if both conditions are met.

Proposing the move, Tory shadow minister Baroness Anelay said: "The government say they are in favour of neighbourhood policing and local accountability. We support that.

"They say they want an overall force that is fit for purpose in the 21st century. We support that too.

"But then they career off on the wrong course and insist that police forces should merge even when local forces are against it."

'Necessary step'

The government opposed the move but lost the vote as the Lords voted 198 to 130 - majority 68.

Home Office Minister Baroness Scotland argued it was the home secretary's job to make strategic decisions and the new plan would curb his powers.

The government had made clear the mergers were the right way to improve services but it realised more time was needed to discuss the best way of doing it, said Lady Scotland.

"Consequently no strategic mergers other than voluntary ones will come into existence before April 2007," she said.

"There are many in the police world who believe that mergers of this sort are a necessary step."